Emit a list results model with just the next link field

For each page of list results fetched, we deserialize list results model but only need the `next_link` (or whatever it may be called). Deserializing all the items is a waste of time and memory like we currently do in https://github.com/Azure/azure-sdk-for-rust/pull/2659 (and even prior to that PR).

It would be great if the emitter generated `pub(crate)` models to use only in the clients that need them that only had the `next_link` field.